THE MANDIBULAR AND HYOID MUSCLES OF MAMMALS. 583 
continuous in front of tlie mandibular division of the fifth 
nerve. The medial portion extends downwards from just 
below the ala temporalis inside MeckeTs cartilage towards 
the mandible; there is an inward bulge from its upper part 
— the Anlage of the tensor veli palatini^ and a long posterioi- 
projection — the Anlage of the tensor tympanic extending 
backwards to the malleus ; the main mass of the medial por- 
tion is the Anlage of the internal pterygoid. The main mass 
Fig. 68. 
Ctmp.m. 
of the lateral portion (Anlage of temporal) has an upward 
projection on the outer side of the Gasserian ganglion, its 
lower end embraces the upper part of the mandible. There 
is a notch on its posterior border — the first indication of 
the separation of a zygomatico-mandibularis and masseter 
portion from the temporal, and an inward projection — the 
Anlage of the external pterygoid, from the hinder part of its 
inner aspect, towards the ala temporalis. 
In a 16 mm. embryo (figs. 46-48 and 68, 69) the ala orbitalis 
and orbito-parietal commissure, the latter with a free posterior 
extremity, are present. The parietal-platte and processus 
alaris are not formed. The ala temporalis has no processus 
ascendens. The Anlage of the mandible has coronoid and 
VOL. 59, PART 4. NEW SERIES. 38 
